Reprographic apparatus



Nov. 25, 1969 ETAL 3,480,359

' REPROGRAPHIC APPARATUS Filed June 14, 1967 INVE/VTORS, LOUIS FREDERICK WILLIAM LAWES NICHOLAS GILBERT SHREEVE NANDOR MIHALIK by W Z ATTORNEYS United States Patent ()1 ice 3,480,359 Patented Nov. 25, 1969 3,480,359 REPROGRAPHIC APPARATUS Louis F. W. Lawes, Walton-on-Thames, Nicholas Gilbert Shreeve, Weybridge, and Nandor Mihalik, Walton-on- Thames, England, assignors to Arlside Limited, Maidenhead, Berkshire, England, a British company Filed June 14, 1967, Ser. No. 645,976 Claims priority, application Great Britain, June 16, 1966,

Int. Cl. G03g /00 U.S. Cl. 3553 11 Claims ABSTRACT OF THE DISCLOSURE A rotatably-mounted drum is provided with an electrostatographic peripherial surface. A developer unit is provided with side walls adjacent the ends of the drum. A stationary bearing member is mated with the edge portions of the developer. Each bearing member is formed with an arcuate end which is concentric to the surface of the drum. At the arcuate ends and laterally thereto the bearing member a sealing strip is frictionally engaged with the drum. A biasing spring located between the side walls and the bearing plate press the sealing strip against the drum thereby preventing the escape of the developer material.

This invention relates to reprographic apparatus, and more particularly to the provision, between a rotating electrostatographic drum of such apparatus and a developer unit thereof, of a seal for preventing the escape of developer material released by the developer unit to cascade over the drum surface and develop a latent image thereon.

It is known in such apparatus to provide a developer unit with a pair of spaced side Walls which extend in parallel planes perpendicular to the axis of rotation of the drum, each side wall having an arcuate edge portion, provided with a felt or similar sealing strip, which bears against the main cylindrical surface of the drum at a respective end thereof, or against a respective cylindrical surface of reduced diameter if the drum is stepped or grooved near its ends to provide such reduced-diameter surfaces. In such an arrangement, the pressure with which the sealing strips bear against the surface or surfaces of the drum, and the consequent frictional drag which resists rotation of the drum, are liable to be considerable, largely because the positioning of the developer unit relative to the drum is in practice subject to a certain amount of tolerance and the design must be such as to provide a suflicient pressure always and thus the possibility of a pressure which is more than, and may be considerably more than, sufficient. g It is an object of the present invention to provide an arrangement whereby an adequate seal is reliably provided but excessive pressure on the drum and consequent excessive friction drag resisting the rotation thereof are avoided.

According to the invention there is provided reprographic apparatus comprising a rotatably-mounted drum, provided with an electrostatographic peripheral surface, and a developer unit provided with two side walls each having a respective edge portion adjacent a respective end of the drum, wherein the said edge portions of the developer unit side walls are spaced apart by a distance greater than the axial length of the drum and there are provided a pair of stationary bearing members each having an edge portion, in closely mating engagement with said edge portion of a respective one of the developer unit side walls, a sealing strip in slidable engagement with a respective end of the drum, and means resiliently urging each bearing member in the axial direction of the drum and thereby effecting said slidable engagement of the respective sealing strip with the respective end of the drum.

An embodiment of the invention is described below with reference to the accompanying drawings, in which:

FIGURE 1 shows an end view of an electrostatographic drum and other associated parts of a reprographic machine, and

FIGURE 2 shows a fragmentary axial sectional view through the drum, taken on the line IIII of FIGURE 1.

The drum showed in FIGURES 1 and 2 and indicated generally by reference 11, comprises a cylindrical member-11a carried at its ends on end plates 11b which, in turn, are mounted on a shaft 12 for rotation therewith. The shaft 12 is rotatably mounted in bearings 13 in side walls 14 and 15 of the machine of which the drum is a part, side wall 14 (shown in FIGURE 2) being omitted in FIGURE 1 for the sake of clarity of the drawing. It will be understood that the shaft 12 carries a chain sprocket or the like (not shown) for the transmission of drive to rotate the shaft 12 and the drum 11, and that the outer cylindrical surface of the drum member 11a is coated with an electrostatographic layer of suitable material.

Adjacent the drum 11 is a developer unit 16 having a pair of spaced parallel side walls 17 (of which only one is shown) each adjacent a respective end of the drum 11. Each side wall 17 is provided with an arcuate edge portion 17 but these edge portions do not co-operate directly with the peripheral surface of the drum 11 to provide a seal (an arrangement which is already known, as noted above). Instead, there are provided a pair of bearing plates 18 each mounted, one adjacent each end of the drum 11, on the shaft 12 by means of a respective hearing 19 which allows the shaft 12 to rotate freely while the bearing plate 18 remains stationary; and to hold the bearing plates stationary each is formed with a spigot 18 which is engaged in a co-operating aperture of the respectively adjacent side wall 14 or 15 of the machine. Each bearing member 18 is formed with an arcuate end which is concentric with the outer peripheral surface of the drum 11, and each bearing plate is provided, at its arcuate end and laterally thereof, with a sealing strip 20 of felt or the like for frictional engagement with the respective end of the drum 11. Each member 18 is further provided with a generally V-shaped leaf spring 21 of which the two arms are each bowed (as may be seen in FIGURE 2) so as to bear against the machine side wall 14 or 15 respectively and press the bearing plate towards the drum and its sealing strip 20 into engagement with the end thereof.

The arcuate edge portions 17 of the side walls 17 of the developer unit 16 have the same curvature as the arcuate ends of the bearing plates 18 and when the developer unit (which for clarity is shown, in the drawings, partly withdrawn from the drum 11) is moved into its operative position, the edge portions 17 bear directly on the arcuate ends of the bearing members 18. It will be appreciated that the edge portions 17' and the arcuate ends of the bearing members 18 can be accurately machined to provide a substantially exact mating with one another, and that the thrust applied by the developer unit, even if it is substantial, is taken by the shaft 12 and not by the drum 11. This thrust, furthermore, does not affect the pressure with which the sealing strips 20 bear against the ends of the drum 11; and the pressure of engagement between the sealing strips 20' and the rotating drum, determined by the springs 21 and not by the developer unit 16, may (while being dependably sufficient) be relatively light so that the frictional drag exerted on the rotating drum is also small.

If, as may advantageously be the case, the side walls (14 and 15 in the foregoing description) are formed with slots in the ends of which the bearings for the drum shaft are disposed and along which the bearings can be drawn (for example, after first removing the developer unit) when it is desired to remove the drum, the spigots 18' of the bearing plates 18 may conveniently be so positioned and dimensioned that they engage in those slots in the side walls, no other apertures in the side walls being then provided for engagement with these spigots.

The developer unit is not shown in detail, though a developer delivery chute 22 and collector plate 2 3 which it comprises are indicated; and means for projecting an optical image onto the drum and for cleaning it and charging it electrostatically before projecting the image onto it are also not shown. However, an arrow A indicates the path along which a sheet of paper is fed (by means, not shown) into engagement with the drum to have transferred to it, from the drum and with the assistance of a corona discharge device 24, an image which has been developed on the drum; and there is also shown means for stripping the paper, with the image transferred to it, from the drum. This stripping means is indicated generally by the reference 25.

It will be understood that, with a drum such as the drum 11 described above, which has no axially projecting shoulders of reduced diameter and of which the cylindrical outer surface is not subject to frictional engagement by the developer unit and can therefore be electrostatographically coated all the way to its ends, the copy paper fed along the path indicated by the arrow A can have transferred to it an image of which the width is as great as the whole axial length of the drum. -It will be further understood that until this image has been fixed, for example by heat-fusing it onto the copy paper, it should not be touched, and that accordingly the stripping means 25, from which the copy paper will be passed to an imagefixing unit (not shown), should not touch the copy paper except outside the maximum width of the image which can be transferred to it. Thus it is preferred to use copy paper which is of greater width than the axial length of the drum, the paper being so fed to the drum that its edges project beyond the ends of the drum in the axial direction thereof.

The stripping means 25 is designed to strip the copy paper from the drum by engaging its projecting edges. For this purpose, the stripping means 25 comprises, at each end of the drum, a pair of co-operating endless belts 26 and 27, supported by sets of rollers 28, 29 and 30, 31 and 32 respectively. Corresponding rollers of the two sets may be mounted on common shafts, except that the two rollers 28, being within the diameter of the drum 11, are mounted on separate stub shafts secured on the respective side walls 14 and 15; and one of the common shafts (as illustrated, a common shaft 33 for the rollers is provided with a chain sprocket or other similar means (not shown) for transmitting drive to the stripping means 25. It will be understood that as the copy paper advances with the drum 11 the ends of its leading edge, projecting laterally of the drum 11, enter the hips between the pairs of moving belts 26 and 27 round the rollers 28 and 30 and are positively gripped between the pairs of belts; thus the paper, across its whole width, is constrained to follow the path defined by the belts over the rollers 31 and between the rollers 29 and 32, the paper being thus stripped off the drum 11.

It will be appreciated that other forms of stripping means may be employed which take advantage of the fact that the seal between the drum and the developer unit is such that the width of paper used can be greater than the axial length of the drum. For example, in a modified form of the illustrated stripping means, the rollers 29, 30, 31 and 32 and the belt 27, may each extend the whole axial length of the drum and beyond, instead of being provided as separate sets of relatively short rollers and narrow belts at each end of the drum. Or, again, the use of belts may be dispensed with, rollers being provided sufiiciently close to one another for such belts "to be unnecessary. For example, there might be provided at each end of the drum a roller like the illustrated roller 30 (but without any belt 27) and thereabove a first roller, like the roller 28 but preferably of somewhat larger diameter, and a further roller, also preferably of larger diameter, in contact wtih the roller corresponding to the roller 30, and rotated thereby, but with a slight clearance from the roller corresponding to the roller 28. Paper fed from the nip between the rollers corresponding to the rollers 28 and 30 would then be advanced against this further roller and carried thereby into the nip between it and the roller corresponding to the roller 30, so that paper would be fed above the lower roller, corresponding to the roller 30, but below the first and further rollers disposed thereabove. If desired, the two upper rollers could have a belt looped around them and engaging the lower roller round part of its circumference, to assist in guiding the paper therearound. It will be understood that many other combinations of various numbers of rollers, and belts if desired, are possible. It will further be appreciated that even if the stripping action is performed by means of stationary stripping fingers, rather than by arragements of rollers, the described way of providing a seal between the drum and the developer unit and of thus enabling the use of paper which is wider than the length of the drum, gives greater freedom in the positioning and shaping of such fingers than would be available if the fingers were required to penetrate into a groove or onto a reduced-diameter shoulder of only limited depth below the main cylindrical surface of the drum.

Returning again to the seal provided for the developer unit, it will be understood that the bearing members 18 constitute a positive stop for the developer unit as it is moved into its operative position, and that thus no other stop means need be provided for positioning the developer unit accurately with respect to the drum. It will be further understood that although, in the illustrated embodiment, the ends of the bearing members and the cooperating edges 17 of the side walls of the developer unit are arcuate, centered on the axis of rotation of the drum, this is not necessary and they could if desired be shaped differently so long as they are of complementary shape with respect to one another. Lastly it will be appreciated that, although the bearing members are described above as being provided with sealing strips 20 of felt or the like, these sealing strips may be formed as integral parts of the bearing members themselves if these are of suitable material, eg Phosphor bronze.

What we claim is:

1. Reprographic apparatus comprising a rotatablymounted drum, provided with an electrostatographic peripheral surface, and a developer unit provided with two side walls each having a respective edge portion adjacent a respective end of the drum, wherein the said edge portions of the developer unit side walls are spaced apart by a distance greater than the axial len th of the drum and there are provided a pair of stationary bearing members each having an edge portion, in closely mating engagement with said edge portion of a respective one of the developer unit side walls, a sealing strip in slidable engagement with a respective end of the drum, and means resiliently urging each bearing member in the axial direction of the drum and thereby effecting said slidable engagement of the respective sealing strip with the respective end of the drum.

2. Reprographic apparatus as claimed in claim 1 and comprising a rotatably mounted shaft having the said drum rigidly mounted thereon for rotation therewith, wherein the bearing members are bearing plates each mounted on the shaft rotatably relative thereto, each bearing plate being provided with means which restrains it against rotation with the shaft and the drum.

3. Reprographic apparatus as claimed in claim 2 and comprising two spaced-apart walls having the said shaft rotatably mounted therein and the drum therebetween, wherein each bearing plate is formed with a projection and each of the said spaced-apart walls has a recess into which a respective one of said projections extends thereby to restrain the respective bearing plate against rotation.

4. Reprographic apparatus as claimed in claim 2, wherein each sealing strip is arcuate, about the said shaft as centre, and engages the respective end of the drum adjacent the peripheral surface of the drum.

5. Reprographic apparatus as claimed in claim 3, wherein each sealing strip is arcuate, about the said shaft as centre, and engages the respective end of the drum adjacent the peripheral surface of the drum.

6. Reprographic apparatus as claimed in claim 2, wherein the said edge portions of the bearing plates and of the developed unit side walls in mating engagement therewith are arcuate, about the said shaft as centre.

7. Reprographic apparatus as claimed in claim 3, wherein the said edge portions of the bearing plates and of the developed unit side walls in mating engagement therewith are arcuate, about the said shaft as centre.

8. Reprographic apparatus as claimed in claim 4, wherein the said edge portions of the bearing plates and of the developed unit side walls in mating engagement therewith are arcuate, about the said shaft as centre.

9. Reprographic apparatus as claimed in claim 5, wherein the said edge portions of the bearing plates and of the developed unit side walls in mating engagement therewith are arcuate, about the said shaft as centre.

10. Reprographic apparatus as claimed in claim 1 and including stripping means for stripping from the drum a sheet of paper having a surface in contact with the peripheral surface of the drum and advancing therewith during rotation thereof, wherein the stripping means is so disposed as to engage the said surface of the sheet only at margins thereof which extend beyond the ends of the drum in the axial direction thereof.

11. Reprographic apparatus as claimed in claim 9 and including stripping means for stripping from the drum a sheet of paper having a surface in contact with the peripheral surface of the drum and advancing therewith during rotation thereof, wherein the stripping means is so disposed as to engage the said surface of the sheet only-at margins thereof which extend beyond the ends of the drum in the axial direction thereof.

References Cited UNITED STATES PATENTS 2,752,833 7/1956 Jacob 35510 3,040,704 6/1962 Bliss 355-16 3,221,622 12/1965 Aser 355-11 NORTON ANSHER, Primary Examiner L. H. MCCORMICK, In, Assistant Examiner US. Cl. X.R. 118637 

